When a police officer indicates Code 4, he is saying the situation is under control, according to the Statesman Journal. Code 4 is part of a coded language used on police and emergency radios transmitted through a police scanner.
Codes 0 through 5 indicate how the police unit is to respond to a call, according to The Oregonian. Code 0 indicates an officer in peril and is a call for help. It generally results in a massive response of other units. Code 1 indicates the officer is to respond at his convenience while Code 2 is a medium priority. Officers receiving a Code 3 call respond with lights and sirens. Code 5 indicates a unit is on a stakeout and that other units are to stay out of the area.